Effects of dietary low protein levels and amino acid patterns on production performance, egg quality and intestinal function in laying hens

This study aimed to investigate the effects of different low-protein (LP) levels and amino acids (AAs) patterns on production performance, egg quality and intestinal function of laying hens. A total of 384 (33-week-old) Hy-Line hens were randomly assigned to control group (CONT, crude protein (CP) 15.91 % + 4AAs), LPF group (CP 14.53 % + 4AAs), LPS group (CP 14.58 % + 8AAs) and LPH group (CP 13.05 % + 8AAs), the formal trial period was 20 weeks. The results showed that the LPF and LPH groups significantly increased feed conversation ratio (FCR) (P < 0.05), the LPS group decreased FCR (P < 0.05). The LPH group significantly decreased laying rate and egg mass (P < 0.05). The plasma reproductive-related hormones anti-Mullerian hormone (AMH), follicle stimulating hormone (FSH) levels significantly decreased in the LPH group (P < 0.05), and leptin (LEP) significantly decreased in LP diets (P < 0.01). Intestinal morphology and function analysis indicated that the LPH group significantly enhanced duodenal villus height-to-crypt depth ratio (V/C) (P < 0.05), up-regulated the expression levels of oligopeptide transporter 1 (PEPT1) and Solute Carrier Family 7 Member 1 (SLC7A1) (P < 0.05). The LPH group had lower short chain fatty acids (SCFAs) content, such as butanoic acid and isovaleric acid (P < 0.05). Additionally, different LP levels and AA patterns significantly altered the cecal microbial composition in phylum and genus levels. At the genus level, Desulfovibriowere was negatively correlated with acetic acid (r = -0.48; P < 0.01), Fournierella were positively correlated with LEP (r = 0.46; P < 0.01), while Methanocorpusculum, Desulfovibrio and Synergistes were negatively correlated with LEP (r = -0.46, -0.51, -0.45; P < 0.01), Rikenellaceae_RC9_gut_group were negatively correlated with FCR (r = -0.47; P < 0.01), and Methanocorpusculum was negatively correlated with EP (r = -0.46, P < 0.01). In conclusion, the LP diet (CP 14.58 % + 8 AAs) improved egg production performance without negatively affecting egg quality, while maintaining intestinal function in laying hens.